1. Field of the Invention
The present invention relates to a storage controller and a logical volume formation method for the storage controller.
2. Description of the Related Art
In the government, the public office, local governments, companies, educational institutions and the like, for example, relatively large storage systems are used to manage data, in order to handle large amounts of various data. Such storage systems are constituted by a storage controller such as a disk array device or the like. A disk array device is configured by disposing a number of disk drives in the form of array, and provides a storage region based on, for example, RAID (Redundant Array of Independent Disks).
A plurality of physical storage devices are generated by grouping a physical storage region provided by a disk drive group. At least one or more logical storage device is formed in each of the physical storage devices. The logical storage devices are allocated to LUN (Logical Unit Number) accessed from a host computer (“host”, hereinafter), and then provided to the host. The host writes data into the logical storage devices or reads the data from the logical storage devices, and thereby executes work processing.
As a first conventional technology, there is known a technology in which, in order to appropriately allocate a logical storage device to the host, a logical storage device is selected, in a concentrated manner, from one physical storage device, or logical storage devices are selected from a plurality of physical storage devices respectively (Japanese Patent Application Laid-Open No. 2004-126867).
As a second conventional technology, there is known a technology in which a logical storage device, which is sequentially accessed, is disposed in a physical storage device having responsive performance to sequential access (Japanese Patent Application Laid-Open No. 2003-271425).
As a third conventional technology, there is known a technology in which logical storage devices are disposed in physical storage devices respectively in accordance with the access frequency (Japanese Patent Application Laid-Open No. H7-93109).
Usually, one logical storage device is allocated to one LUN. However, the storage capacity required by a host has been increasing recently, thus there is the case in which a plurality of logical storage devices are allocated to one LUN. Specifically, one logical volume that is recognized as a target of access from the host is virtually constructed as an assembly of a plurality of logical storage devices. For example, in the case where the storage capacity required by the host is so large that one logical storage device is not enough, sometimes one logical volume is constructed with a plurality of logical storage devices.
On the other hand, there are a plurality of types of access patterns when the host accesses a logical volume. One of the types is random access and one of the other types is sequential access. In the case of the random access, the host averagely accesses all address spaces within a logical volume. In the case of the sequential access, the host accesses a specific address space within a logical volume in a concentrated manner.
However, neither one of the above conventional technologies considers virtual construction of one logical volume from a plurality of logical storage devices. Moreover, neither one of the above conventional technologies considers how the destination to allocate a logical storage device is determined in accordance with different types of access patterns. Each of the above conventional technologies lacks consideration of the random access in particular.
Furthermore, even if there are accesses from the same host, the access pattern might change depending on the time zone. For example, depending on the quality of the work processing executed on the host, an access pattern in a certain time zone might change to a random access, and an access pattern in a different zone might change to a sequential access.
Therefore, responsive performance at the time of a random access cannot be improved by only determining the destination to allocate a logical storage device in the case of only the sequential access, or determining the destination to allocate a logical storage device based on the access frequency.